Feasibility of producing 225Ac via thermal neutron irradiation of 226Ra: A systematic theoretical study

Abstract

With a suitable half-life and abundant radiolabeling strategy, ²²⁵Ac has become one of the most promising radionuclides in the area of targeted alpha therapy. However, limited radionuclide supply is threatening the development of ²²⁵Ac related endoradiotherapy dramatically. As the parent nuclide of ²²⁵Ac, ²²⁹Th can be produced via ²²⁶Ra(3n, 2β)²²⁹Th reaction in a nuclear reactor. However, related practice has not been conducted in large scale, since the nuclear reaction pathway for producing ²²⁹Th is complicated. In this work, the feasibility of producing ²²⁵Ac/²²⁹Th in a reactor was confirmed by systematic theoretical calculations, and a procedure that combines irradiation with separation process was proposed. The results show that 176 MBq of ²²⁹Th can be produced by irradiating 1.0 g of ²²⁶Ra with a neutron flux density of 1 × 10¹⁵ n cm⁻² s⁻¹ for 90 days. This will generate 150 MBq of ²²⁵Ac monthly from a radionuclide generator, which is sufficient for the single treatment cycle of 200 patients each year considering the radioactivity loss in radiochemical separation, transfer and radiolabeling process. In addition, this irradiation process will also produce 37.8 GBq ²²⁷Ac for the preparation of ²²⁷Ac-²²⁷Th-²²³Ra generator. In general, the production of ²²⁵Ac by neutron irradiation of ²²⁶Ra in reactor is practicable and holds potential to alleviate the shortage of current supply of ²²⁵Ac.